Showing papers by "Edward G. Lakatta published in 2022"

A Remarkable Adaptive Paradigm Of Heart Performance And Protection Emerges In Response To The Constitutive Challenge of Marked Cardiac-Specific Overexpression Of Adenylyl Cyclase Type 8

Abstract: Adult mice with a marked increase in Adenylyl cyclase (AC) activity due to cardio-specific over expression of adenylyl cyclase (AC) type VIII (TGAC8) have an incessantly cardiac work load adapt to this chronic, severe cAMP stress for up to a year without signs of heart failure and without excessive mortality compared to wild-type littermates (WT). Here we focused on mechanisms that underly the TGAC8 adaptive paradigm. Although TGAC8 mice had a 30% increase in both HR and cardiac output, a 23% increase in EF (echocardiography), neither total LV mass nor pathologic hypertrophy biomarkers differed by genotype. Compared to WT the LV cavity volume was reduced in TGAC8, but was encased by thicker LV walls, harboring populations of both smaller cardiac myocytes, and small non-cardiac interstitial cells having increased nuclear EdU labeling. Protein synthesis, proteosome activity, autophagy, Nrf-2 and Hsp90α proteins were also increased in TGAC8 vs WT, but super-oxide radicals did not differ. Despite an apparently marked increased energy demand due to a chronically increased cardiac workload in the context of a chronically increased HR and EF, steady-state LV ATP and phosphocreatine in vivo did not differ in TGAC8 vs WT. Further Acc2, known to suppress fatty acid oxidation and to increase aerobic glycolysis in the context of enhanced utilization of the pentose phosphate shunt, and NADH/NADPH cycling were both elevated in TGAC8 vs WT mice. Unbiased omics unveiled additional genotypic differences in the potential mechanisms involved in the chronically increased TGAC8 heart performance and the adaptive paradigm in response to this chronic stress. 2,323 transcripts and 2,184 proteins, spanning a wide array of biological processes and molecular functions in numerous cellular compartments, including over 250 canonical signaling pathways, that integrate stress responses, cytokine and T cell receptor signaling, immune responses, ROS scavenging, protection from apoptosis, and nutrient sensing, were activated in TGAC8 vs WT. Several adaptive mechanisms that limit cAMP/PKA signaling were also activated in TGAC8. Thus, in addition to markedly increased cardiac work, the chronic, intense AC-PKA-Ca2+ signaling within the adult TGAC8 heart concurrently activates a consilience of adaptive mechanisms within the TGAC8 LV that resemble survival mechanisms within cancer cells.

Metformin Attenuates Hyperglycaemia-Stimulated Pro-Fibrotic Gene Expression in Adventitial Fibroblasts via Inhibition of Discoidin Domain Receptor 2

Abstract: Molecular mechanisms underlying the diverse therapeutic effects of anti-diabetic metformin, beyond its anti-hyperglycaemic effects, remain largely unclear. Metformin is reported to reduce the long-term complications of diabetes, including cardiovascular fibrosis and remodelling. Our recent investigations show that Discoidin Domain Receptor 2 (DDR2), a collagen receptor tyrosine kinase, has an obligate regulatory role in collagen type I gene expression in cardiac and vascular adventitial fibroblasts, and that it may be a molecular link between arterial fibrosis and metabolic syndrome in rhesus monkeys. Using gene knockdown and over-expression approaches, the present study examined whether DDR2 is a target of metformin, and whether, by targeting DDR2, it inhibits fibronectin and collagen expression in vascular adventitial fibroblasts exposed to hyperglycaemic conditions. Metformin was found to attenuate hyperglycaemia-induced increase in DDR2 mRNA and protein expression by inhibiting TGF-β1/ Smad2/3 signalling that mediates the stimulatory effect of hyperglycaemia on DDR2 expression. Metformin also inhibited DDR2-dependent expression of fibronectin and collagen, indicating that it regulates these matrix proteins via DDR2 inhibition. The findings identify DDR2, a major mediator of cardiovascular remodelling, as a molecular target of metformin, thereby uncovering the molecular basis of its protective role in vascular fibrosis, and possibly, cardiac fibrosis associated with diabetic cardiomyopathy.

Emergence of heartbeat frailty in advanced age I: perspectives from life-long EKG recordings in adult mice

Abstract: Abstract The combined influences of sinoatrial nodal (SAN) pacemaker cell automaticity and its response to autonomic input determine the heart’s beating interval variability and mean beating rate. To determine the intrinsic SAN and autonomic signatures buried within EKG RR interval time series change in advanced age, we measured RR interval variability before and during double autonomic blockade at 3-month intervals from 6 months of age until the end of life in long-lived (those that achieved the total cohort median life span of 24 months and beyond) C57/BL6 mice. Prior to 21 months of age, time-dependent changes in intrinsic RR interval variability and mean RR interval were relatively minor. Between 21 and 30 months of age, however, marked changes emerged in intrinsic SAN RR interval variability signatures, pointing to a reduction in the kinetics of pacemaker clock mechanisms, leading to reduced synchronization of molecular functions within and among SAN cells. This loss of high-frequency signal processing within intrinsic SAN signatures resulted in a marked increase in the mean intrinsic RR interval. The impact of autonomic signatures on RR interval variability were net sympathetic and partially compensated for the reduced kinetics of the intrinsic SAN RR interval variability signatures, and partially, but not completely, shifted the EKG RR time series intervals to a more youthful pattern. Cross-sectional analyses of other subsets of C57/BL6 ages indicated that at or beyond the median life span of our longitudinal cohort, noncardiac, constitutional, whole-body frailty was increased, energetic efficiency was reduced, and the respiratory exchange ratio increased. We interpret the progressive reduction in kinetics in intrinsic SAN RR interval variability signatures in this context of whole-body frailty beyond 21 months of age to be a manifestation of “heartbeat frailty.”

Effect of Cardiotonic Steroid Marinobufagenin on Vascular Remodeling and Cognitive Impairment in Young Dahl-S Rats

Abstract: The hypertensive response in Dahl salt-sensitive (DSS) rats on a high-salt (HS) diet is accompanied by central arterial stiffening (CAS), a risk factor for dementia, and heightened levels of a prohypertensive and profibrotic factor, the endogenous Na/K-ATPase inhibitor marinobufagenin (MBG). We studied the effect of the in vivo administration of MBG or HS diet on blood pressure (BP), CAS, and behavioral function in young DSS rats and normotensive Sprague–Dawley rats (SD), the genetic background for DSS rats. Eight-week-old male SD and DSS rats were given an HS diet (8% NaCl, n = 18/group) or a low-salt diet (LS; 0.1% NaCl, n = 14–18/group) for 8 weeks or MBG (50 µg/kg/day, n = 15–18/group) administered via osmotic minipumps for 4 weeks in the presence of the LS diet. The MBG-treated groups received the LS diet. The systolic BP (SBP); the aortic pulse wave velocity (aPWV), a marker of CAS; MBG levels; spatial memory, measured by a water maze task; and tissue collection for the histochemical analysis were assessed at the end of the experiment. DSS-LS rats had higher SBP, higher aPWV, and poorer spatial memory than SD-LS rats. The administration of stressors HS and MBG increased aPWV, SBP, and aortic wall collagen abundance in both strains vs. their LS controls. In SD rats, HS or MBG administration did not affect heart parameters, as assessed by ECHO vs. the SD-LS control. In DSS rats, impaired whole-heart structure and function were observed after HS diet administration in DSS-HS vs. DSS-LS rats. MBG treatment did not affect the ECHO parameters in DSS-MBG vs. DSS-LS rats. The HS diet led to an increase in endogenous plasma and urine MBG levels in both SD and DSS groups. Thus, the prohypertensive and profibrotic effect of HS diet might be partially attributed to an increase in MBG. The prohypertensive and profibrotic functions of MBG were pronounced in both DSS and SD rats, although quantitative PCR revealed that different profiles of profibrotic genes in DSS and SD rats was activated after MBG or HS administration. Spatial memory was not affected by HS diet or MBG treatment in either SD or DSS rats. Impaired cognitive function was associated with higher BP, CAS, and cardiovascular remodeling in young DSS-LS rats, as compared to young SD-LS rats. MBG and HS had similar effects on the cardiovascular system and its function in DSS and SD rats, although the rate of change in SD rats was lower than in DSS rats. The absence of a cumulative effect of increased aPWV and BP on spatial memory can be explained by the cerebrovascular and brain plasticity in young rats, which help the animals to tolerate CAS elevated by HS and MBG and to counterbalance the profibrotic effect of heightened MBG.

Beneficial effects of AT1 antagonists treatment, losartan, on cardiovascular and cognitive function on aged male Dahl salt sensitive rats

Abstract: Cardiovascular diseases and hypertension are the major contributors to the pathogenesis of vascular dementia. The Dahl salt‐sensitive (DSS) rat model is characterized by age‐associated cardiovascular remodeling and the development of central arterial stiffness (CAS) in the presence of renin‐angiotensin system disbalance, accompanied by cognitive decline. We hypothesized, that the anti‐hypertensive treatment, antagonist for angiotensin II receptors losartan (LOS), via reducing CAS, will improve cardiovascular parameters and cognitive function in aged DSS male rats.

A remarkable adaptive paradigm of heart performance and protection emerges in response to marked cardiac-specific overexpression of ADCY8

Abstract: Adult (3 month) mice with cardiac-specific overexpression of adenylyl cyclase (AC) type VIII (TGAC8) adapt to an increased cAMP-induced cardiac workload (~30% increases in heart rate, ejection fraction and cardiac output) for up to a year without signs of heart failure or excessive mortality. Here, we show classical cardiac hypertrophy markers were absent in TGAC8, and that total left ventricular (LV) mass was not increased: a reduced LV cavity volume in TGAC8 was encased by thicker LV walls harboring an increased number of small cardiac myocytes, and a network of small interstitial proliferative non-cardiac myocytes compared to wild type (WT) littermates; Protein synthesis, proteosome activity, and autophagy were enhanced in TGAC8 vs WT, and Nrf-2, Hsp90α, and ACC2 protein levels were increased. Despite increased energy demands in vivo LV ATP and phosphocreatine levels in TGAC8 did not differ from WT. Unbiased omics analyses identified more than 2,000 transcripts and proteins, comprising a broad array of biological processes across multiple cellular compartments, which differed by genotype; compared to WT, in TGAC8 there was a shift from fatty acid oxidation to aerobic glycolysis in the context of increased utilization of the pentose phosphate shunt and nucleotide synthesis. Thus, marked overexpression of AC8 engages complex, coordinate adaptation "circuity" that has evolved in mammalian cells to defend against stress that threatens health or life (elements of which have already been shown to be central to cardiac ischemic pre-conditioning and exercise endurance cardiac conditioning) that may be of biological significance to allow for proper healing in disease states such as infarction or failure of the heart.

Changes in cAMP signaling are associated with age-related downregulation of spontaneously beating atrial tissue energetic indices

Abstract: The prevalence of atria-related diseases increases exponentially with age and is associated with ATP supply-to-demand imbalances. Because evidence suggests that cAMP regulates ATP supply-to-demand, we explored aged-associated alterations in atrial ATP supply-to-demand balance and its correlation with cAMP levels. Right atrial tissues driven by spontaneous sinoatrial node impulses were isolated from aged (22–26 months) and adult (3–4 months) C57/BL6 mice. ATP demand increased by addition of isoproterenol or 3-Isobutyl-1-methylxanthine (IBMX) and decreased by application of carbachol. Each drug was administrated at the dose that led to a maximal change in beating rate (Xmax) and to 50% of that maximal change in adult tissue (X50). cAMP, NADH, NAD + NADH, and ATP levels were measured in the same tissue. The tight correlation between cAMP levels and the beating rate (i.e., the ATP demand) demonstrated in adult atria was altered in aged atria. cAMP levels were lower in aged compared to adult atrial tissue exposed to X50 of ISO or IBMX, but this difference narrowed at Xmax. Neither ATP nor NADH levels correlated with ATP demand in either adult or aged atria. Baseline NADH levels were lower in aged as compared to adult atria, but were restored by drug perturbations that increased cAMP levels. Reduction in Ca2+-activated adenylyl cyclase-induced decreased cAMP and prolongation of the spontaneous beat interval of adult atrial tissue to their baseline levels in aged tissue, brought energetics indices to baseline levels in aged tissue. Thus, cAMP regulates right atrial ATP supply-to-demand matching and can restore age-associated ATP supply-to-demand imbalance.

Ankle‐Brachial Index and Energy Production in People Without Peripheral Artery Disease: The BLSA

Abstract: Background Lower ankle‐brachial index (ABI) values within the 0.90 to 1.40 range are associated with poorer mitochondrial oxidative capacity of thigh muscles in cross‐sectional analyses. Whether ABI decline is associated with greater declines in thigh muscle oxidative capacity with aging is unknown. Method and Results We analyzed data from 228 participants (100 men) of the BLSA (Baltimore Longitudinal Study of Aging), aged 39 to 97 years, with an ABI between 0.9 and 1.40 at baseline and at follow‐up (mean follow‐up period of 2.8 years). We examined mitochondrial oxidative capacity of the left thigh muscle, by measuring the postexercise phosphocreatine recovery rate constant (kPCr) from phosphorus‐31 magnetic resonance spectroscopy. Greater kPCr indicated higher mitochondrial oxidative capacity. Although kPCr was available on the left leg only, ABI was measured in both legs. Longitudinal rates of change (Change) of left and right ABI and kPCr of the left thigh muscle were estimated using linear mixed effects models, and their association was analyzed by standardized multiple linear regressions. In multivariate analysis including sex, age, baseline kPCr, both left and right baseline ABI, and ABI change in both legs, (kPCr)Change was directly associated with ipsilateral (left) (ABI)Change (standardized [STD]‐β=0.14; P=0.0168) but not with contralateral (right) (ABI)Change (P=0.22). Adjusting for traditional cardiovascular risk factors, this association remained significant (STD‐β=0.18; P=0.0051). (kPCr)Change was steeper in White race participants (STD‐β=0.16; P=0.0122) and body mass index (STD‐β=0.13; P=0.0479). There was no significant association with current smoking status (P=0.63), fasting glucose (P=0.28), heart rate (P=0.67), mean blood pressure (P=0.78), and low‐density lipoprotein (P=0.75), high‐density lipoprotein (P=0.82), or triglycerides (P=0.15). Conclusions In people without peripheral arterial disease, greater decline in ABI over time, but not baseline ABI, was associated with faster decline in thigh mitochondrial oxidative capacity in the ipsilateral leg. Further studies are needed to examine whether early interventions that improve lower extremity muscle perfusion can improve and prevent the decline of muscle energetics.

Proteomic Landscape and Deduced Functions of the Cardiac 14-3-3 Protein Interactome

Abstract: Rationale: The 14-3-3 protein family is known to interact with many proteins in non-cardiac cell types to regulate multiple signaling pathways, particularly those relating to energy and protein homeostasis; and the 14-3-3 network is a therapeutic target of critical metabolic and proteostatic signaling in cancer and neurological diseases. Although the heart is critically sensitive to nutrient and energy alterations, and multiple signaling pathways coordinate to maintain the cardiac cell homeostasis, neither the structure of cardiac 14-3-3 protein interactome, nor potential functional roles of 14-3-3 protein–protein interactions (PPIs) in heart has been explored. Objective: To establish the comprehensive landscape and characterize the functional role of cardiac 14-3-3 PPIs. Methods and Results: We evaluated both RNA expression and protein abundance of 14-3-3 isoforms in mouse heart, followed by co-immunoprecipitation of 14-3-3 proteins and mass spectrometry in left ventricle. We identified 52 proteins comprising the cardiac 14-3-3 interactome. Multiple bioinformatic analyses indicated that more than half of the proteins bound to 14-3-3 are related to mitochondria; and the deduced functions of the mitochondrial 14-3-3 network are to regulate cardiac ATP production via interactions with mitochondrial inner membrane proteins, especially those in mitochondrial complex I. Binding to ribosomal proteins, 14-3-3 proteins likely coordinate protein synthesis and protein quality control. Localizations of 14-3-3 proteins to mitochondria and ribosome were validated via immunofluorescence assays. The deduced function of cardiac 14-3-3 PPIs is to regulate cardiac metabolic homeostasis and proteostasis. Conclusions: Thus, the cardiac 14-3-3 interactome may be a potential therapeutic target in cardiovascular metabolic and proteostatic disease states, as it already is in cancer therapy.

Inflammatory Role of Milk Fat Globule–Epidermal Growth Factor VIII in Age‐Associated Arterial Remodeling

Abstract: Background Age‐associated aortic remodeling includes a marked increase in intimal medial thickness (IMT), associated with signs of inflammation. Although aortic wall milk fat globule–epidermal growth factor VIII (MFG‐E8) increases with age, and is associated with aortic inflammation, it is not known whether MFG‐E8 is required for the age‐associated increase in aortic IMT. Here, we tested whether MFG‐E8 is required for the age‐associated increase in aortic IMT. Methods and Results To determine the role of MFG‐E8 in the age‐associated increase of IMT, we compared aortic remodeling in adult (20‐week) and aged (96‐week) MFG‐E8 (−/−) knockout and age matched wild‐type (WT) littermate mice. The average aortic IMT increased with age in the WT from 50±10 to 70±20 μm (P<0.0001) but did not significantly increase with age in MFG‐E8 knockout mice. Because angiotensin II signaling is implicated as a driver of age‐associated increase in IMT, we infused 30‐week‐old MFG‐E8 knockout and age‐matched littermate WT mice with angiotensin II or saline via osmotic mini‐pumps to determine whether MFG‐E8 is required for angiotensin II–induced aortic remodeling. (1) In WT mice, angiotensin II infusion substantially increased IMT, elastic lamina degradation, collagen deposition, and the proliferation of vascular smooth muscle cells; in contrast, these effects were significantly reduced in MFG‐E8 KO mice; (2) On a molecular level, angiotensin II treatment significantly increased the activation and expression of matrix metalloproteinase type 2, transforming growth factor beta 1, and its downstream signaling molecule phosphorylated mother against decapentaplegic homolog 2, and collagen type I production in WT mice; however, in the MFG‐E8 knockout mice, these molecular effects were significantly reduced; and (3) in WT mice, angiotensin II increased levels of aortic inflammatory markers phosphorylated nuclear factor‐kappa beta p65, monocyte chemoattractant protein 1, tumor necrosis factor alpha, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 molecular expression, while in contrast, these inflammatory markers did not change in knockout mice. Conclusions Thus, MFG‐E8 is required for both age‐associated proinflammatory aortic remodeling and also for the angiotensin II–dependent induction in younger mice of an aortic inflammatory phenotype observed in advanced age. Targeting MFG‐E8 would be a novel molecular approach to curb adverse arterial remodeling.

Clusters of risk factors in metabolic syndrome and their influence on central blood pressure in a global study

Abstract: The effect of metabolic syndrome (MetS) and clusters of its components on central blood pressure (CBP) has not been well characterized. We aimed to describe the effect of MetS and clusters of its components on CBP in a large population and to identify whether this effect differs in men and women. We studied 15,609 volunteers (43% women) from 10 cohorts worldwide who participated in the Metabolic syndrome and Artery REsearch Consortium. MetS was defined according to the NCEP-ATP III criteria (GHTBW, glucose, high-density lipoprotein cholesterol, triglyceride, blood pressure, waist circumference). CBP was measured noninvasively and acquired from pulse wave analysis by applanation tonometry. MetS was associated with a 50% greater odds of having higher CSBP. After controlling for age, male sex, non HDL cholesterol, diabetes mellitus, and mean arterial pressure, only specific clusters of MetS components were associated with a higher CSBP; and some of them were significant in women but not in men. We identified "risky clusters" of MetS variables associated with high CSBP. Future studies are needed to confirm they identify subjects at high risk of accelerated arterial aging and, thus, need more intensive clinical management.

Adenosine Reduces Sinoatrial Node Cell AP Firing Rate by uncoupling its Membrane and Calcium Clocks

Abstract: The spontaneous action potential (AP) firing rate of sinoatrial nodal cells (SANC) is regulated by a system of intracellular Ca2+ and membrane ion current clocks driven by Ca2+-calmodulin-activated adenylyl cyclase-protein kinase A (PKA) signaling. The mean AP cycle length (APCL) and APCL variability inform on the effectiveness of clock coupling. Endogenous ATP metabolite adenosine (ado) binds to adenosine receptors that couple to Gi protein-coupled receptors, reducing spontaneous AP firing rate via Gβγ signaling that activates an membrane-clock outward current, IKACh. Ado also inhibits adenylyl cyclase activity via Giα signaling, impacting cAMP-mediated PKA-dependent protein phosphorylation and intracellular Ca2+ cycling. We hypothesize that in addition to IKAdo activation, ado signaling impacts Ca2+ via Giα signaling and that both effects reduce AP firing rate by reducing the effectiveness of the Ca2+ and membrane clock coupling. To this end, we measured Ca2+ and membrane potential characteristics in enzymatically isolated single rabbit SANC. 10 µM ado substantially increased both the mean APCL (on average by 43%, n=10) and AP beat-to-beat variability from 5.1±1.7% to 7.2±2.0% (n=10) measured via membrane potential and 5.0±2.2 to 10.6±5.9 (n=40) measured via Ca2+ (assessed as the coefficient of variability, CV=SD/mean). These effects were mediated by hyperpolarization of the maximum diastolic membrane potential (membrane clock effect) and suppression of diastolic spontaneous, local Ca2+ releases (LCRs) (Ca2+ clock effect): as LCR size distributions shifted from larger to smaller values, the time of LCR occurrence during diastolic depolarization (LCR period) became prolonged, and the ensemble LCR Ca2+ signal became reduced. The tight linear relationship of coupling between LCR period to the APCL in the presence of ado “drifted” upward and leftward, i.e. for a given LCR period, APCL was prolonged, becoming non-linear indicating clock uncoupling. An extreme case of uncoupling occurred at higher ado concentrations (>100 µM): small stochastic LCRs of the Ca2+ clock failed to self-organize and synchronize to the membrane clock, thus creating a failed attempt to generate an AP resulting in arrhythmia and cessation of AP firing. Thus, the effects of ado to activate Gβγ and IKACh, Ado and to activate Giα, suppressing adenylyl cyclase activity, both contribute to the ado-induced increase in the mean APCL and APCL variability by reducing the fidelity of clock coupling and AP firing rate.

Abstract P2034: Photobiomodulation Accelerates Wound Healing In Heart Tissue

Abstract: Cardiovascular diseases and aging induce stress on the heart, resulting in heart wall thickness and stiffness associated with increased fibrosis. The sinoatrial node (SAN) is the heart’s natural pacemaker composed of a fibrous tissue matrix with a heterogenous cellular population. With aging, activated fibroblasts can create scar tissue, thus commonly resulting in sick sinus syndrome (SSS) and arrhythmias. SSS is produced by idiopathic degeneration of the SAN, requiring implantation of electronic pacemakers. Phototherapy or photobiomodulation (PBM) is a technique with many therapeutic properties that has been applied clinically to treat various forms of tissue pathology. Although there has been evidence that PBM has positive effects on the heart to improve cardiac function and prevent infarction, its age associated changes during wound healing are unknown. This study uses timelapse microscopy and red light (630 nm) or near-infrared (NIR, 810 nm) PBM on SAN support cells (SANspc) isolated from 2 months (2mo) and 2 years (2y) old mice during in vitro wound healing. With an average initial gap width of 540 μm, the kinetics and extent of wound closure are measured for each of the SANspc age and treatment groups. Nonirradiated SANspc served as controls. Aging slowed kinetics and increased the extent of wound healing by an average of 1.87 hours earlier than that of the 2mo-SANspc (p < 0.05). Irradiation with red light induces a significantly faster scale of closure for the gap width to close between ½ and ¾ by 0.25 and 0.68 hours, in 2mo- and 2y-SANspc respectively, compared to their corresponding age control. With red irradiation, 2y-SANspc resulted in a significantly faster scale of closure of 0.52 hours compared to 2mo-SANspc. Irradiation with NIR resulted in the opposite effect in both age groups, in which the scale of closure for the wound slowed significantly (0.19 and 0.71 hours in the 2mo- and 2y-SANspc, respectively). In conclusion, these data suggests that SANspc migration and proliferation capacity is faster with aging and red irradiation increases wound closing effect in both age groups. Thus, the enhanced wound healing induced by PBM may be an attractive therapeutic approach to target cardiac fibrosis and promote cardiac remodeling in the aging heart.

Dilated hypertrophic phenotype of the carotid artery is associated with accelerated age-associated central arterial stiffening

Abstract: Hypertrophic carotid geometric phenotypes (h-CGP) are predictors of incident cardiovascular disease (CVD). While arterial aging is hypothesized as a contributor to this associated risk, the association of CGPs with chronological age is not clear. In this manuscript we examine whether hypertrophic CGPs represent accelerated biological, rather than chronological, aging by examining their association with carotid-femoral pulse wave velocity (PWV), the hallmark of arterial aging. We analyzed data from 5516 participants of the SardiNIA study with a wide range of age at baseline (20–101 years), and a median follow-up time of 13 years (mean 11.5 years; maximum 17.9 years). Baseline CGPs were defined based on the common carotid lumen diameter, wall thickness, and their ratio. Subject-specific rates of change of PWV, blood pressure parameters, body mass index, glucose, and lipids were estimated using linear mixed effects models. Compared to those with typical(t-) CGP, those with dilated hypertrophy (dh-) CGP had a greater longitudinal increase in PWV; this increase was significantly greater among older individuals and men. The greater PWV longitudinal increase in dh-CGP remained significant after adjusting for baseline values and rates of change of covariates. Dilated hypertrophic CGP is independently associated with accelerated increase in age-associated arterial stiffening over time, with a strong association in men than in women. Future studies are needed to examine if this association mediates the increased risk for CVD observed in individuals with hypertrophic cardiac remodelling and the role of retarding it to reduce this risk. • Individuals with dilated hypertrophic geometric phenotypes of the common carotid artery (increased age- and sex-specific wall thickness and lumen diameter) have greater future central arterial stiffening, independently of other determinants of arterial stiffening. • The dilated hypertrophic phenotype group has a greater age-specific arterial dilation, wall thickening, and stiffness (the arterial aging triad). This suggests that this phenotype is a form of accelerated aging that might explain the worse clinic outcomes observed in this group. • Understanding the natural history of the carotid geometric phenotype across the lifespan and the determinants of the deleterious progression towards the dilated hypertrophic phenotype are needed to develop interventions that reduce the adverse clinical outcomes associated with it.

708 patterns of biological aging of the heart and their prognostic value: the sardi-nia study

Abstract: As people age at different rates, the concept of biological age has been introduced as a measure of functional deterioration. Associations of echocardiographic traits with age were analyzed to detect different biological aging rates of the heart and their prognostic value. Echocardiographic left ventricular mass, geometry, left atrial volume, diastolic function, and aortic root size were measured in 3817 adults (58% females). Sex-specific correlations of age with six cardiac traits were assessed in 2614 healthy subjects. According to two-sided 95% tolerance intervals, three patterns of heart aging rates were identified in the whole cohort: slow aging pattern (n=287), normal aging pattern (n=2669), and accelerated aging pattern (n=796). The phenotypic (biological) age of the heart (HeartPhAge) was estimated from the cardiac traits by multiple linear regression. Cardiovascular and non-cardiovascular incident events at follow-up (46 months (IQR 34–64 months) were grouped into three endpoints and analyzed in survival analyses. Compared to chronological age, HeartPhAge was nine years younger (p<0.0001) in the slow aging pattern, similar in the normal pattern, and three years older (p<0.0001) in the accelerated pattern. The incidence of all endpoints was higher in the accelerated pattern than in the normal and slow aging patterns (p<0.0001 to p=0.0003). In Cox proportional-hazards analysis, the heart aging patterns significantly predicted all endpoints in both the whole cohort and the healthy subset, independent of chronological age and risk factors. Heart aging patterns reflect the rate of biological aging and independently predict cardiovascular and non-cardiovascular events.

Adenosine reduces sinoatrial node cell action potential firing rate by uncoupling its membrane and calcium clocks

Abstract: The spontaneous action potential (AP) firing rate of sinoatrial nodal cells (SANC) is regulated by a system of intracellular Ca2+ and membrane ion current clocks driven by Ca2+-calmodulin-activated adenylyl cyclase-protein kinase-A signaling. The mean AP-cycle length (APCL) and APCL variability inform on the effectiveness of clock coupling. Endogenous ATP metabolite adenosine binds to adenosine receptors (A1, A3) that couple to Gi protein-coupled receptors, reducing spontaneous AP firing rate via Gβγ signaling that activates IKAch,Ado. Adenosine also inhibits adenylyl cyclase activity via Gαi signaling, impacting cAMP-mediated protein kinase-A-dependent protein phosphorylation. We hypothesize that in addition to IKAch,Ado activation, adenosine impacts also Ca2+ via Gαi signaling and that both effects reduce AP firing rate by reducing the effectiveness of the Ca2+ and membrane clock coupling. To this end, we measured Ca2+ and membrane potential characteristics in enzymatically isolated single rabbit SANC. 10 µM adenosine substantially increased both the mean APCL (on average by 43%, n = 10) and AP beat-to-beat variability from 5.1 ± 1.7% to 7.2 ± 2.0% (n = 10) measured via membrane potential and 5.0 ± 2.2% to 10.6 ± 5.9% (n = 40) measured via Ca2+ (assessed as the coefficient of variability = SD/mean). These effects were mediated by hyperpolarization of the maximum diastolic membrane potential (membrane clock effect) and suppression of diastolic local Ca2+releases (LCRs) (Ca2+-clock effect): as LCR size distributions shifted to smaller values, the time of LCR occurrence during diastolic depolarization (LCR period) became prolonged, and the ensemble LCR signal became reduced. The tight linear relationship of coupling between LCR period to the APCL in the presence of adenosine “drifted” upward and leftward, i.e. for a given LCR period, APCL was prolonged, becoming non-linear indicating clock uncoupling. An extreme case of uncoupling occurred at higher adenosine concentrations (>100 µM): small stochastic LCRs failed to self-organize and synchronize to the membrane clock, thus creating a failed attempt to generate an AP resulting in arrhythmia and cessation of AP firing. Thus, the effects of adenosine to activate Gβγ and IKACh,Ado and to activate Gαi, suppressing adenylyl cyclase activity, both contribute to the adenosine-induced increase in the mean APCL and APCL variability by reducing the fidelity of clock coupling and AP firing rate.

Treatment with losartan, an AT1 receptor blocker, improves cognitive and cardiovascular function in a Dahl salt‐sensitive rat model of age‐associated vascular dementia.

Abstract: Dementia is characterized by progressive cognitive impairment (CI), which is accompanied by decline in reasoning, planning and memory. Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia and affect mainly the aging population. Even on a normal salt diet, Dahl salt‐sensitive (DSS) rats exhibit age‐associated hypertension and CI. We hypothesized, that anti‐hypertensive treatment with the angiotensin II receptor blocker losartan (LOS) would improve cardiovascular and cognitive function in aged DSS rats.

Bioactive Steroid Marinobufagenin in a Mouse Model of Early‐Stage Alzheimer's Disease

Abstract: Alzheimer’s disease (AD) is characterized by brain amyloid beta plaque formation, neuroinflammation and neuronal degradation, which lead to cognitive impairment and decline in normal circadian rhythm (CR). Bioactive steroid marinobufagenin (MBG) modulates neuroinflammation. In 16‐mo old double transgenic APPswe/PS1dE9 AD mice with advanced AD, amyloid precursor protein (APP) and interleukin 6 (IL6) mRNAs were upregulated vs. wild type (WT) control, and treatment with MBG reduced mRNA expression. Here, we investigated whether treatment with MBG at early‐stage AD may impact AD development in this AD mouse model.

Cognitive impairment is associated with cardiovascular remodeling in the mouse model of Alzheimer’s disease

Abstract: Double‐mutant mice (APPswe/PS1dE9; 2xTg‐AD) represent a model of Alzheimer’s disease (AD). 2xTg‐AD mice develop progressive accumulation of amyloid plaques and cognitive impairment (CI) with age in >12 months old animals. The aim of the present study was to investigate the associations of CI and cardiovascular function in 2xTg‐AD mice.

Emergence of Heartbeat Frailty in Advanced Age: Perspectives from Life-Long EKG Recordings in Mice

Abstract: SAN failure, aka sick-sinus syndrome, which features sinus bradycardia, SAN impulse pauses, and irregularity of RR interval rhythms are manifestations of SAN cell dysfunction that increases exponentially with advanced age, i.e., SAN frailty. Abnormalities in intrinsic RR interval variability may be the earliest signatures of SAN cell dysfunction leading to SAN frailty in late life. We measured RR interval variability within EKG timeseries prior to and during double autonomic blockade in long-lived C57/BL6 mice at 3 month intervals from 6 months of age until the end of life. Long-lived mice (those that achieved the median cohort lifespan of 24 months and beyond) displayed relatively minor changes in intrinsic RR interval variability prior to 21 months of age. Between 21 and 30 months of age, marked changes in intrinsic RR interval variability signatures in time, frequency, non-linear, and fragmentation domains result in a marked increase in the mean intrinsic RR interval. The effects of autonomic input partially compensated for the prolongation of the mean RR interval by impacting the age-associated deterioration in the RR interval variability signatures toward a youthful pattern. Cross-sectional analyses of other subsets of mice at ages at or beyond the median life span of our longitudinal cohort demonstrated increased non-cardiac, constitutional, whole body frailty, a decrease in energetic efficiency, and an increase in respiratory exchange ratio. In this context, we interpret the progressive increase in intrinsic RR interval variability beyond 21 months of age to be an indication of heartbeat frailty.

Losartan, angiotensin ii type 1 receptor blocker, reduced aortic stiffness and improved cognitive function in dahl salt sensitive rat model of age-associated vascular dementia

Abstract: Objective: Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia. The Dahl salt sensitive (Dahl-S) rat model is characterized by the development of central arterial stiffness (CAS), hypertension and cognitive decline with age on a normal salt diet. We hypothesized that treatment with losartan (LOS), angiotensin II type 1 receptor (AT1R) blocker, via reduction of blood pressure (BP) and CAS, will improve cognitive function in aged Dahl-S rats. Design and method: Male Dahl-S rats (n = 30) were kept on a normal salt diet (0.5% NaCl) for the duration of the study. Baseline measurements were taken at 3- and/or 6-mo of age following by the treatment with LOS in drinking water (30 mg/kg/day, n = 14) or control treatment (n = 16) for 6-mo. Measurements were taken every 3 months and included systolic and diastolic BP (SBP, DBP), pulse wave velocity (PWV), a measure of CAS, left ventricular posterior wall thickness in diastole (LVPWd), fractional shortening (FS) and LV mass (by echocardiography). At 12-mo of age the rats were tested in operant chambers using a simple reaction task to assess attention and impulsivity, and in elevated plus maze (EPM) to assess anxiety-like behavior. Statistical analyses were performed using 2-way ANOVA and t-test. Data are presented as mean ± SEM. Results: Prior to the treatment, LOS and control groups did not display differences in any parameter analyzed. Following the treatment, LOS rats had lower SBP, DBP, PWV, thinner LVPWd, higher FS and smaller LV mass at 9- and 12-mo of age vs. control group (Fig.1A-F). In the reaction task, LOS rats demonstrated more correct responses and fewer premature responses. The LOS rats exhibited lower anxiety level, because they spent more time in the open arm of EPM vs. control rats (Fig.1G,H). Conclusions: Beneficial effect of LOS on cognitive function in aged male Dahl-S rats was associated with the improvement of cardiovascular function and remodeling. The CAS stabilizing and BP reduction by LOS treatment was associated with improved attentional performance, lower impulsivity and lower anxiety. The mechanistic basis of these effects of LOS on cognition via cerebrovascular and brain changes will be further investigated.

Cognitive impairment is associated with increased central arterial stiffness in an animal model of chronic kidney disease.

Abstract: The prevalence of cognitive impairment (CI) and dementia in end‐stage chronic kidney disease (CKD) has been estimated at 30‐60%. Cardiovascular diseases (CVD) including increased central arterial stiffness (CAS) accompany CKD development and contribute to CI. Elevated pulse wave velocity (PWV) is associated with higher mortality in CVD and CKD independently of blood pressure (BP). Marinobufagenin (MBG) is a pro‐fibrotic factor, which increases in CKD and contributes to CAS. The aim of this study was to determine whether CKD potentiates CI development via CAS and cardiovascular remodeling in a rat model of CKD.

Abstract 515: Inhibiting Dpp4 In Senescent Vascular Smooth Muscle Cells Suppresses A Coagulation Program

Abstract: In older persons, senescent vascular smooth muscle cells (VSMCs) express increased levels of senescence-associated secretory phenotype (SASP) factors such as cytokines, chemokines, adhesion molecules, matrix-remodeling enzymes, and angiogenic factors. The SASP contributes to destabilizing the plaque cap, suggesting that VSMC senescence promotes disease development. As a result of their prevalence in many diseases, major efforts are underway to develop therapies directed at senescent cells (senotherapies). Dipeptidyl Peptidase 4 (DPP4), a serine protease, was elevated on the plasma membrane of senescent fibroblasts. While the effect of DPP4 on VSMCs is not well understood, DPP4 inhibitors such as Vildagliptin are clinically used to treat diabetes, and in animal models, gliptins reduced atherosclerosis and inflammation independently of DPP4’s canonical role in glucose metabolism. We hypothesized that DPP4 inhibitors may reduce the progression and burden of atherosclerosis by preventing DPP4 enzymatic function on senescent VSMCs. Towards this end, we discovered that DPP4 protein levels and enzymatic activity increased in senescent human VSMCs (hVSMCs) senescence. We also found elevated DPP4 in human atherosclerotic plaques, and high levels of DPP4 colocalized with the senescence marker p16 in murine atherosclerosis. Strikingly, silencing DPP4 in senescent hVSMCs increased cell death and caspase activity. Proteomic analysis of conditioned media from senescent hVSMCs treated with DPP4 inhibitors revealed a reduction in numerous complement and coagulation factors, indicating that DPP4 partially governs hemostasis and the proteolytic events that promote thrombotic signaling. We propose that DPP4 inhibition suppresses the pro-coagulation/complement phenotype of senescent hVSMCs to disrupt their function and improve vascular disease progression.